1. Technical Field
The present invention relates to a separable laminated container, of which an inner layer is separated from an outer layer and shrinks according to the decrease of the liquid content, and the related arts.
2. Background Art
A separable laminated container is made up of an outer layer and an inner layer which are made of synthetic resin. The inner layer is separably laminated to the outer layer. The separable laminated container is normally used in the sealed state with a pump installed to a neck portion thereof. As the liquid content is poured out by the pump, the inner layer is separated from the outer layer and shrinks according to the decrease of the liquid content. In order to smoothly conduct the shrinkage of the inner layer, the outer layer is provided with an air suction hole.
As one of methods of forming such an air suction hole, a method in which the air suction hole is formed by partially fusing the outer layer of the separable laminated container has been proposed (for example, Japanese Published Unexamined Patent Application No. H06-345069). In this method, the inner layer of the laminated container is made of resin having melting point higher than that of the outer layer and the resin of the outer layer is only fused to form the air suction hole by fusion means which is set at a temperature higher than the melting point of the outer layer and lower than the melting point of the inner layer.
However, the method of forming the air suction hole as mentioned above has following problems.
In case of a little difference between the melting points of the inner layer and the outer layer, it is quite difficult to fuse the outer layer only. Therefore, a predetermined difference in temperature between the melting points of the inner layer and the outer layer is required, thereby restricting the selection of resins used for the inner layer and the outer layer.
Since the air suction hole is formed by fusing the resin of the outer layer by the fusion means, it is difficult to sharply form the air suction hole into a predetermined configuration. Therefore, a finishing is necessary to make the hole neat.
Temperature control is necessary to keep the fusion means in a constant temperature range, thereby complicating the device.
One of the objects of the present invention is to provide a method of forming an air suction hole in an outer layer in a desired configuration and the device.
There is a separable laminated container in which an outer layer and an inner layer are partially bonded as disclosed in Japanese Published Unexamined Patent Application No. H04-339759, Japanese Published Unexamined Patent Application No. H05-310265, or the like. The position where the outer layer and the inner layer are bonded has been considered variously. For example, the bonded portion is provided linearly along the longitudinal direction of the separable laminated container.
By the way, the separable laminated container is normally made in a method as described below.
First, a laminated parison or laminated preform (hereinafter, referred to as the laminated parison) having a laminated structure corresponding to the separable laminated container to be manufactured is molded by extrusion molding. During this molding, a bonded area extending the axial direction is provided in a predetermined position in such a manner as to allow the separation between the outer layer and the inner layer besides the bonded area. Then, the laminated parison is set in the mold and molded into a desired bottle-like configuration by blow molding in such a manner as to have an air suction hole in the outer layer.
For making sure to introduce air through the air suction hole, the position of the air suction hole should be shifted from the bonded area. When the diameter of the air suction hole is equal to or smaller than the width of the bonded area, overlap between the air suction hole and the bonded area results the blockage of the air suction hole so that air can not be introduced into a space the outer layer and the inner layer and the inner layer can not shrink.
However, since there is no mark indicating the position of the bonded area in the conventional separable laminated container, the air suction hole is sometimes formed to be overlapped with the bonded area.
Another one of the objects of the present invention is to provide a separable laminated container allowing an air suction hole to be positively positioned at a portion shifted from the bonded area.
By the way, to smoothly separate the inner layer from the outer layer according to the decrease of the liquid content in the separable laminated container, pre-separation is made before filling the container with the liquid content, for example, as disclosed in Japanese Published Unexamined Patent Application No. 06-345069. The conventional pre-separation is made by blowing air through the air suction hole of the separable laminated container to separate the inner layer from the outer layer, then blowing air into the container through the neck, and deaerating a space between the inner layer and the outer layer through the air suction hole so that the inner layer is returned in such a manner as to cling to the inner surface of the outer layer.
However, in the conventional separable laminated container, the inner layer is made of synthetic resin having a melting point higher than that of the material of the outer layer and flexural modules between 10,000 kg/cm2 and 50,000 kg/cm2 (measured by ASTM D790 method of measurement) so as to have good distortion resistance, that is, higher elasticity. Therefore, to smoothly separate the inner layer according to the decrease of the liquid content, the inner layer must be completely separated over the entire laminated area during the pre-separation.
For that, a predetermined amount of air according to the dimensions of the container should be blown between the layers. Therefore, there is a problem that the separation can not be completed overall when the control of blowing is mistook.
Further, a control unit is necessary for controlling the amount of air, thereby complicating the device.
As well known, since the outer layer and the inner layer should be made of resin having lower bond properties for the purpose of separating the inner layer from the outer layer, the inner layer and the outer layer are not completely bonded to each other at a pinch-off portion formed at a bottom of the blow-molded container. This causes a cracking of the pinch-off portion and a slit between the layers due to a separation, thereby causing a sealing defect.
Under the circumstances mentioned above, the synthetic resin having good distortion resistance, that is, higher elasticity as described above further facilitates the defect. There is a problem that the container entraps moisture between the inner layer and outer layer from the sealing defect when the container is used in a damp area.
In the conventional pre-separation, the inner layer is separated from the outer layer and then returned in the original position. At this point, the inner layer is compressed against the outer layer, thereby making the separability between the layers low.
Another one of the objects of the present invention is to provide a separable laminated container in which an inner layer can be easily separated from an outer layer, and further another one of the objects is to provide a method and device of pre-separation which is easily completed by partly separating the inner layer with a small amount of air.
Since, once separated from the outer layer, the inner layer is returned in such a manner as to cling to the inner surface of the outer layer in the conventional pre-separation, the level to which the pre-separation is finished does not appear externally so that it is difficult to inspect the level.
Another one of the objects of the present invention is to provide a separable laminated container which allowing the easy inspection of the level to which the pre-separation is finished.
In case of a container for liquid, since the ratio of the amount of liquid content to the capacity of the container is generally constant, larger capacity of the container makes an upper space after filled with the liquid content larger so that the level is sometimes lowered to a lower portion of a shoulder or near an upper end of the drum portion of the container.
In case of installing a pump to the neck of the container, taking into consideration the rise of the level due to the insertion of the pump and troubles for inserting the pump, the liquid content is filled in the container in such a manner as to have larger upper space, thereby sometimes lowering the level.
As the upper space is increased and the level of the liquid is lowered to the lower portion of the shoulder or near the upper end of the drum of the container as mentioned above, the water face of the liquid content waves and the splash of the liquid content becomes violent, thereby bubbling the liquid content and/or generating gases depending on the kind of the liquid content.
As the level of the liquid content is lowered to the upper end of the drum of the container, in case of transparent or translucent container, this gives consumers the impression that the content is less than the indicated amount of content even when the container is filled with the content of amount equal to the indicated amount. Even in case of opaque container, it also gives consumers the same impression because of the degree of the splash of the liquid content when swinging the container.
Another one of the objects of the present invention is to provide a pre-separation method allowing smaller upper space when a container is in the filled state, and a container with a pump allowing smaller upper space.